Tissue separating catheter assembly and method

ABSTRACT

A tissue-separating catheter assembly comprises a rotatable shaft, having a distal shaft portion, and a tissue separator device extending along the shaft. The tissue separator device has a distal separator part at the distal shaft portion movable between a retracted state, towards the distal shaft portion, and an outwardly extending, operational state, away from the distal shaft portion. A pivot joint may be used to pivotally connect the distal separator end to the distal shaft portion. The distal shaft portion may comprise a distally-facing transition surface at a proximal end of the distal shaft portion. First and second energizable tissue separator elements may be used at the transition surface and the tip of the device, respectively.

CROSS REFERENCE TO OTHER APPLICATIONS

[0001] This application is related to U.S. patent application Ser. No.10/045,657 filed 7 Nov. 2001 and entitled Tissue Separator Assembly AndMethod. This application is also related to the following two patentapplications filed on the same date as this application: TissueLocalizing And Separating Assembly, attorney Docket No. 1019-1; TissueSeparating And Localizing Catheter Assembly, attorney Docket No. ARTM1018-1. See also: (1) U.S. Pat. No. 6,179,860 issued 30 Jan. 2001 andentitled Target Tissue Localization Device And Method, (2) InternationalPublication No. WO 00/10471 published 2 Mar. 2000 and entitled TargetTissue Localization Device And Method, (3) U.S. Pat. No. 6,221,006issued 24 Apr. 2001 and entitled Entrapping Apparatus And Method ForUse, (4) International Publication No. WO 99/39648 published 12 Aug.1999 and entitled Entrapping Apparatus And Method For Use, (5) U.S.patent application Ser. No. 09/588,278 filed 5 Jun. 2000 and entitledTissue Removal Methods And Apparatus, (6) International Publication No.WO 00/74561 published 14 Dec. 2000 and entitled Tissue Removal MethodsAnd Apparatus, and (7) U.S. patent application Ser. No. 09/844,661 filed27 Apr. 2001 and entitled Intraoperative Tissue Treatment Methods.

BACKGROUND OF THE INVENTION

[0002] Cancer presently results in over one thousand five hundred deathsevery day in the United States (550,000 deaths every year). Therapymodalities for cancer are plentiful and continued to be researched withvigor. Still, the preferred treatment continues to be physical removalof the cancer. When applicable, surgical removal is preferred (breast,colon, brain, lung, kidney, etc.). Open, excisional, surgical removal isoften extremely invasive so that efforts to remove cancerous tissue inless invasive ways continue, but have not yet been perfected.

[0003] The only cure for cancer continues to be the early diagnosis andsubsequent early treatment. As cancer therapies continue at earlierstages of diagnosis, the cancerous tissue being operated on is alsosmaller. Early removal of the smaller cancers demand new techniques forremoval and obliteration of these less invasive cancers.

[0004] There is a variety of techniques that attempt to accomplish lessinvasive cancer therapy, but so far without sufficiently improvedresults. For example, the ABBI system from U.S. Surgical Corporation andthe Site Select system from ImaGyn Corporation, attempt to accomplishless invasive cancer therapy. However, conventional techniques, incontrast with Minimally Invasive Surgery (MIS) techniques, require alarge core (that is more than about 15 mm diameter) incision.Additionally, the Mammotome system from Johnson and Johnson and MIBBsystem from U.S. Surgical Corporation also require large core (overabout 4 mm diameter) access to accomplish biopsy.

[0005] A convention held by the American Society of Surgical Oncologistson Mar. 13, 2000 reported that conventional stereotactic core biopsy(SCB) procedures fall short in providing definitive answers to detailprecise surgical regimens after this SCB type vacuum assisted biopsy,especially with ductile carcinoma in situ (DCIS). Apparently thesepercutaneous systems damage “normal” tissue cells so that it isdifficult to determine if the cells are “normal damaged” cells or earlypre-cancerous (e.g. Atypical Ductal Hyerplasia (ADH)) cells.

[0006] A study presented by Dr. Ollila et al. from the University ofNorth Carolina, Chapel Hill, demonstrated that histology and pathologyis compromised using these conventional techniques because of the damagedone to the removed tissue specimens. Hence, for many reasons, includingthe fact that DCIS is becoming more detectable and hence more prevalentin breast cancer diagnosis in the U.S., there is a growing need toimprove upon conventional vacuum assisted core biopsy systems.

SUMMARY OF THE INVENTION

[0007] A first aspect of the invention is directed to atissue-separating catheter assembly comprising a rotatable shaft, havinga tip and a distal shaft portion, and a tissue separator deviceextending along the shaft. The tissue separator device has a distalseparator part at the distal shaft portion movable between a retractedstate, towards the distal shaft portion, and an outwardly extending,operational state, away from the distal shaft portion. The distal shaftportion comprises a distally-facing transition surface at a proximal endof the distal shaft portion. The transition surface extends radiallyoutwardly and longitudinally away from said tip. A first energizabletissue separator element is at the transition surface. A secondenergizable tissue separator element is at or near the tip. The firstand second tissue separator elements are adapted to aid movement of thedistal shaft portion through tissue and to a target site.

[0008] A second aspect of the invention is directed to atissue-separating catheter assembly comprising a shaft, having a distalshaft portion, and a tissue separator device extending along the shaft.The tissue separator device has a distal separator part at the distalshaft portion movable between a retracted state, towards the distalshaft portion, and an outwardly extending, operational state, away fromthe distal shaft portion. The assembly also comprises first and secondenergizable tissue separator means for aiding movement of the distalshaft portion through tissue and to a target site. The first and secondmovement aiding means are located generally proximal and distal of thedistal separator part of the tissue separator device, respectively.

[0009] A third aspect of the invention is directed to a method foraccessing a target site within a patient. A tissue-separating catheterassembly is selected. The tissue-separating catheter assembly comprisesa shaft, having a distal shaft portion, and a tissue separator deviceextending along the shaft. The tissue separator device has a distalseparator part at the distal shaft portion movable between a retractedstate, towards the distal shaft portion, and an outwardly extending,operational state, away from the distal shaft portion. The assembly alsocomprises first and second energizable tissue separator means for aidingmovement of the distal shaft portion through tissue and to a targetsite. The first and second movement aiding means are located proximaland distal of the distal separator part of the tissue separator device,respectively. The distal shaft portion, and the first and secondenergizable tissue separator elements and the distal separator parttherewith, are directed through tissue and to a target site. The firstand second energizable tissue separator elements are energize during atleast a part of the directing step so to aid movement of the distalshaft portion through the tissue and to the target site.

[0010] A fourth aspect of the invention is directed to atissue-separating catheter assembly comprising a rotatable shaft, havinga distal shaft portion, and a tissue separator device extending alongthe shaft. The tissue separator device has a distal separator part atthe distal shaft portion movable between a retracted state, towards thedistal shaft portion, and an outwardly extending, operational state,away from the distal shaft portion. The distal separator part comprisesa distal separator end. A pivot joint pivotally connects the distalseparator end to the distal shaft portion so that said distal separatorend effectively pivots freely at the pivot joint as the distal separatorpart moves between the retracted and operational states. The pivot jointmay include a ball-type element housed within a cavity the defined bythe distal shaft portion.

[0011] A fifth aspect of the invention is directed to a method forincreasing the volume of a separated tissue section from a patient. Atissue-separating catheter assembly generally made according to thefourth aspect of the invention is selected. The distal shaft portion,and the distal separator part and the pivot joint therewith, aredirected through tissue and to a target site. The distal separator partis moved through tissue from the retracted state to an operational statewith the distal separator part pivoting at the pivot joint. The shaft isrotated thereby causing the distal separator part in the operationalstate to pass through tissue and create a separated tissue section. Theseparated tissue section is removed from the patient.

[0012] A sixth aspect of the invention is directed to a method foraccessing a target site within a patient. A tissue-separating catheterassembly is selected. The catheter assembly comprises: a rotatable shafthaving a distal shaft portion; a tissue separator device extending alongthe shaft and having a plurality of distal separator parts at the distalshaft, each said distal separator part being positionable at an exposed,retracted state towards the distal shaft portion, at least one of saiddistal separator parts being movable to an outwardly extending,operational state spaced apart from the distal shaft portion; and atleast some of said distal separator parts being energizable in saidexposed, retracted state. The distal shaft portion and the distalseparator parts therewith are directed through tissue and to a targetsite while the distal separator parts are in said exposed, retractedstates. At least some of said distal separator parts are energizedduring at least a part of the directing step so to aid movement of thedistal shaft portion through the tissue and to the target site.

[0013] Other features and advantages of the invention will appear fromthe following description in which the preferred embodiments have beenset forth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a partially schematic overall view of a tissue separatorassembly made according to the invention with portions of the handleremoved for clarity;

[0015]FIG. 1A is a simplified cross-sectional view taken along line1A-1A of FIG. 1 showing the engagement of a pin within a slot in thelead nut mounted to the lead screw;

[0016]FIG. 2 is schematic view of portions of the drive elements of theassembly of FIG. 1;

[0017]FIG. 3 is a simplified cross-sectional view of the catheterassembly taken along line 3-3 of FIG. 1;

[0018]FIG. 4 is an oblique view of the housing half of FIG. 1 togetherwith the drive screw, drive nut and an L-shaped actuator connected toand movable with the drive nut;

[0019]FIGS. 5 and 6 show the handle and catheter assembly of FIG. 1after the actuator has moved from the position of FIG. 1 and theactuator extension has pushed the separator wire pusher screw in adistal direction causing the separator wire to move radially outwardly;

[0020]FIG. 7 is a simplified the end view of the block and the pusherscrew just after the pusher screw has exited the slot in the blockshowing the off-vertical orientation of the pusher screw;

[0021]FIG. 8 illustrates the proximal end of the lead screw, which isvisible from outside the housing, and a rotary position indicator markedthereon corresponding to the position of the separator wire in FIG. 10;

[0022]FIGS. 9 and 10 illustrate the structure of FIGS. 5 and 6 after thedrive screw has moved the actuator distally causing the lead nut torotate the lead screw, catheter shaft and separator wire therewith about540 degrees to create a separated tissue section;

[0023]FIGS. 11 and 12 illustrate the manual actuation of tissue sectionholding elements;

[0024]FIG. 13 is a simplified view of certain of the components of FIG.12;

[0025]FIG. 14 is a cross-sectional view of the catheter taken along line14-14 of FIG. 13;

[0026]FIGS. 15 and 16 illustrate the manual actuation of a tubularbraided element to surround the separated tissue section;

[0027]FIG. 17 is a simplified view of certain of the components of FIG.16;

[0028]FIG. 18 is enlarged side view of the distal end of an alternativeembodiment of the catheter assembly of FIG. 1;

[0029]FIG. 19 is a side view of a modified embodiment of the distal endof the catheter assembly of FIG. 18;

[0030]FIG. 20 is a schematic illustration showing the difference in sizebetween the separated tissue sections of the embodiments of FIGS. 18 and19;

[0031]FIG. 21 is an enlarged top view taken along line 21-21 of FIG. 18;

[0032]FIG. 22 is an enlarged cross-sectional view taken along the line22-22 of FIG. 21;

[0033]FIG. 23 is a cross-sectional view taken along line 23-23 of FIG.18;

[0034] FIGS. 24A-24H are simplified side views of different embodimentsof the guide element/transition surface of FIG. 18;

[0035]FIG. 25 is an overall view of the distal end of the catheterassembly of FIG. 18 illustrating a hook wire/tissue holding element in adeployed condition;

[0036]FIG. 26 is a cross-sectional view of a portion of the shaft ofFIG. 25;

[0037]FIG. 27 is a somewhat simplified cross-sectional view of thestructure of FIG. 25 with the separator wire portion in a radiallyretracted state;

[0038]FIG. 27A is a somewhat simplified cross-sectional view of thestructure of FIG. 25 with the separator wire portion in a radiallyextended state;

[0039]FIG. 28 illustrates a further embodiment of the invention of FIG.18 including three separator wire portions, one of which is shown in theoperational state; and

[0040]FIG. 29A is a simplified end view of the structure of FIG. 28suggesting three equally-spaced separator wire portions, each in theirretracted states;

[0041]FIG. 29B is a view similar to FIG. 29A but with one separator wireportion in an operational state;

[0042]FIG. 30 is a simplified schematic illustration of atissue-penetrating assembly;

[0043]FIG. 31 is an overall view of a tissue localizing and separatingassembly made according to the invention including a tissue separatorassembly, a coupler and a tissue localization assembly, the localizationdevice of the tissue localization assembly being in an expandedcondition at a target site within a patient;

[0044]FIG. 32 is an enlarged view of a portion of the assembly of FIG.31 illustrating a loop at the distal end of the coupler being engagedwith the proximal end of the tissue localization assembly;

[0045]FIGS. 33 and 34 illustrate the distal end of the coupler and theproximal end of the tissue localization assembly of FIG. 31 joined toone another;

[0046]FIG. 35 illustrates the distal movement of the tissue separatorassembly causing the joined ends of FIGS. 33 and 34 to be moved into thecatheter assembly thereby docking the tissue localization assembly tothe tissue separator assembly;

[0047] FIGS. 35A-35C are simplified drawings showing the movement of anindicator tube, secured to the elongate coupler, through an opening inthe proximal end of the handle;

[0048]FIG. 36 is an enlarged view of the distal portion of the assemblyof FIG. 35 after the separator wire portion has been radially expandedand rotated and after the hook wire has been deployed to engage theseparated tissue section;

[0049]FIG. 37 illustrates the assembly of FIG. 36 after the catheterassembly sleeve has been moved proximally a short distance to expose thedistal end of the tubular braided element;

[0050]FIG. 38 is a somewhat idealized illustration of the movement ofthe tubular braided element in a distal direction within a patient withthe tubular braided element initially generally following the outline ofthe separated tissue section and its outer end generally axially alignedwith the localization device;

[0051]FIG. 39 illustrates the assembly of FIG. 38 after having beenremoved from the patient with the outer end of the tubular braidedelement returned to its relaxed state;

[0052]FIG. 40 illustrates the shape of a tubular braided material afterit has been stretched over a cylindrical mandrel having an enlargedcentral portion;

[0053]FIG. 41 illustrates the structure of FIG. 40 after one end of themandrel and the tubular braided material has been dipped into a siliconecompound;

[0054]FIG. 42 illustrates the open mesh end of the dipped tubularbraided material, after the silicone has been cured and removed from themandrel, being pulled back into the dipped end to create a tubularbraided element;

[0055]FIG. 43 illustrates the resulting tubular braided element beingmounted to the distal end of the actuator tube;

[0056]FIG. 44 shows the proximal end of the tubular braided elementbeing secured to the distal end of the actuator tube by a length of heatshrink tubing; and

[0057]FIG. 45 illustrates the tubular braided element secured to theactuator tube.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0058]FIGS. 1 and 2 illustrate a tissue separator assembly 10 used toseparate target tissue from surrounding tissue, typically within apatient's breast. The removal of target tissue may be for diagnostic ortherapeutic purposes. The assembly 10 includes a catheter assembly 12extending from a handle 14. Introduction of catheter assembly 12 intothe patient, typically through the skin, is preferably aided by the useof, for example, a trocar or an RF tip to provide a suitable paththrough the tissue. A stepper motor 16 is connected to handle 14 by adrive cable 18 and a drive cable connector 20 mounted to the handlehousing 22. Note that in the Figs. only one-half of handle housing 22 isshown; the other housing half is substantially similar. RF energy issupplied to catheter assembly 12 from an RF source 24, along drive cable18 and to the interior of handle 14. A controller 26 controls theoperation of stepper motor 16 as well as RF source 24, such as speed ofoperation and energy level. Controller 26 also receives appropriatefeedback signals from handle 14 and catheter assembly 12, such as tissuetemperature, resistance force signals, tissue impedance, rotaryorientation, and so forth.

[0059] Drive cable 18 is connected to and rotates a drive screw 28rotatably mounted within handle 14 at a fixed axial location by drivescrew supports 30, 32. A drive nut 34 is threadably mounted to drivescrew 28. An L-shaped actuator 36 is secured to drive nut 34. Actuator36, see FIG. 4, includes a generally horizontal base portion 38 and agenerally vertical upright portion 40 sized and configured to movewithin handle 14 parallel to the axis of drive screw 28. Therefore,rotation of drive screw 28 by stepper motor 16 causes actuator 36 toslide within housing 22 from the initial position of FIG. 1 to theposition of FIG. 10. Reverse and reciprocating movement is alsopossible.

[0060] Catheter assembly 12 includes in introducer sheath 42 mounted toand extending from housing 22. Catheter assembly 12 also includes anactuator tube 43, discussed below with reference to FIGS. 14-17, passingthrough sheath 42 and a shaft 44 passing through tube 43. See FIG. 3.Shaft 44 has a distal portion 46 extending distally of the distal end 48of sheath 42 and a proximal portion 50 extending into the interior ofhandle 14. Proximal portion 50 is secured to and rotates with a leadscrew 52. Accordingly, shaft 44 rotates with lead screw 52. Lead screw52 is mounted within housing 22 in a manner so that it can rotate butnot move axially within housing 22. A tissue separator device 54 extendsalong shaft 44 and has a separator wire portion 56 secured to the distalend 58 of shaft 44. The separator wire 56 is positioned externally ofdistal portion 46. The majority of tissue separator device 54 is in theform of a wire and extends through an axial bore 60 formed in shaft 44.The separator device 54 has a radially extending pusher screw 62 at itsproximal end. The proximal end of shaft 44 has an axially extending slot64, see FIG. 2, through which pusher screw 62 extends. Accordingly,pushing pusher screw 62 distally, that is to the left in the Figs.,causes tissue separator wire 56 to move outwardly from its radiallycontracted condition of FIG. 1 to its radially extended condition ofFIGS. 5 and 6. This radially outwardly movement is typicallyaccomplished at the target site within the patient, typically apatient's breast. To aid movement of separator wire through the tissue,wire 56 is supplied with RF energy from RF source 24. Other applicationsof energy, such as mechanical reciprocation or mechanical vibration, canalso be used.

[0061] The axial movement of pusher screw 62 is caused by the axialmovement of actuator 36. Actuator 36 has an extension 66 extendingdistally from upright portion 40. Extension 66 has a downwardly formeddistal end 68 aligned with pusher screw 62. The initial axial movementof actuator 40, caused by the rotation of drive screw 28 by steppermotor 16, closes a small gap 70 (see FIG. 2) between distal end 68 andpusher screw 62. This small gap permits the initiation of anelectrosurgical arc prior to the outwardly radial movement of separatorwire 56. Continued distal movement of actuator 36 moves pusher screw 62distally causing separator wire 56 to bow outwardly to the position ofFIGS. 5 and 6. FIGS. 5 and 6 (but not FIG. 1) show the use of a supportblock 72, which is a part of housing 22, to support the distal end oflead screw 52 and the proximal end of shaft 44. Support block 72 has anaxially extending slot 74, see FIGS. 5 and 7, which initially housespusher screw 62. At the time separator wire 56 is fully extended, pusherscrew 62 exits slot 74 and the distal end 68 of extension 66, which hasa chamfered face, causes pusher screw 62, along with shaft 44, to beginrotating to the off-vertical position of FIG. 7. At the same timeupright portion 40 of actuator 36 closes gap 73 (see FIG. 2) andcontacts a lead nut 75 threadably mounted on lead screw 52. Ananti-rotation pin 76 extends from upright portion 40 of actuator 36 andis housed within a U-shaped slot 78 formed in lead nut 74, see FIG. 1A,to prevent lead nut 74 from rotating around lead screw 52 as lead nut 74it is moved axially by actuator 36. Instead, the axial movement ofactuator 36 causes lead screw 52 to rotate thus rotating shaft 44.Assembly 10 is configured so that shaft 44 rotates about 540 degrees toensure a tissue section 80 is completely separated from the surroundingtissue by the passage of separator wire 56 through the tissue. Theradial position of separator wire 56 can be easily determined by lookingat the proximal end 82 of lead screw 52, which is exposed throughhousing 22. See FIG. 8. Proximal end 82 has a rotary position indicator84 formed thereon corresponding to the rotary position of separator wire56.

[0062] The above-described sequence of events, according to thisdisclosed embodiment, proceeds automatically once initiated by a user.Of course operation of the device, including one or more of extension ofseparator wire 56, rotation of shaft 44 and energizing wire 56, can beterminated manually or automatically based on, for example, anunexpected resistance to the rotation of shaft 44.

[0063] Assembly 10 also includes a T-pusher device 86 having a pair ofpusher tabs 88 extending laterally outwardly from slots formed inhousing 22. See FIGS. 11-13. After shaft 44 has completed its rotation,the user begins pushing tabs 88 distally. This causes an extension 90 ofdevice 86 to rotate a flipper cam 92 about a pivot pin 94; flipper cam92 is connected to the proximal ends of a pair of tissue section holdingelements 96. Holding elements 96 are in the form of wires passingthrough axial bores 98 formed in shaft 44 as shown in FIG. 3. The distalends of holding elements 96 are preformed hook wires 100, preferablymade of a shape memory material such as Nitinol, which pass throughopenings formed in distal portion 46 of shaft 44 and engage separatedtissue section 80 to help secure tissue section 80 to distal portion 46of shaft 44.

[0064] Device 86 includes a distal end 102 connected to the proximal endof actuator tube 43. Thus, the movement of device 86 causes tube 43 tomove distally within introducer sheath 42. At this point, that is withhook wires 100 deployed as an FIGS. 11-13, a tubular braided element104, see FIGS. 14-17, secured to the distal end of actuator tube 43, isstill fully housed within sheath 42. Further distal movement of device86 causes tubular braided element 104 to extend outwardly past distalend 48 of sheath 42 to the position of FIGS. 15-17. The purpose oftubular braided element 104 is to surround separated tissue section 80by passing along the dissection plane between the separated tissuesection and the surrounding tissue. The open outer end 106 of element104 naturally expands radially as it is pushed axially through thetissue. To aid the proper initial radial expansion of element 104, shaft44 has an outwardly tapered guide surface 108, formed on a guide element110, positioned adjacent to distal end 48 of introducer shaft 42. Theproper radial expansion of element 104 may also be aided by the shapethat element 104 takes when in its relaxed state. See, for example, thediscussion of tubular braided element 104 with regard to FIGS. 40-45.Guide element 110 has a slot in its proximal surface into which theproximal end of separator wire 56 passes when in the radially expandedcondition of FIG. 9; this helps to keep separator wire 56 from foldingover during rotation. If desired, outer end 106 of tubular braidedelement 104 could include a drawstring or other type of closure element.The separated tissue section 80, now substantially enclosed withintubular braided element 104 and secured to distal portion 46 of shaft 44by hook wires 100, may be removed from the patient.

[0065] With the present invention separated tissue section 80 retainsmost if not all of its physical integrity once removed from the patient.Also, the use of tubular braided element 104, especially when it issealed or otherwise impermeable to the passage of material, helps toreduce the possibility of seeding diseased tissue along the tissue trackduring removal of separated tissue section 80.

[0066] FIGS. 18-29B illustrate further embodiments of the invention withlike reference numerals referring to like elements. FIG. 18 is anenlarged side view of the distal end 120 of alternative embodiment ofthe catheter assembly 12 of FIG. 1. Referring now also to FIGS. 21, 22and 27, separator wire portion 56 is seen to include a distal end 122.Distal end 122 terminates at a ball-type element 124 (see FIG. 22)housed within a cavity 126 defined within distal portion 46 of shaft 44at the tip 136 of the distal portion to form a pivot joint 128. Theprovision of pivot joint 128 permits distal end 122 to effectively pivotfreely as separator wire portion 56 is moved between the operational andretracted states. In addition to reducing stresses and improving thefatigue characteristics of distal end 122 of separator wire portion 56,the use of pivot joint 128 helps to increase the volume of the separatedtissue section removed from the patient for the same distance of travelof tissue separator device 54. This increase in volume may beappreciated by comparing the embodiments of FIGS. 18 and 19. In the FIG.19 embodiment, the distal end 122 of separator wire portion 56 isrigidly or otherwise non-pivotally secured to distal portion 46 of shaft44. FIG. 20 illustrates the increased volume of separated tissue section80A resulting from the embodiment of FIG. 18 to the reduced volume,separated tissue section 80B from the embodiment of FIG. 19. In thisexample the volume of separated tissue section 80A has been calculatedto be about 50 percent greater than the volume of separated tissuesection 80B for the same distance of travel of tissue separator device54.

[0067] Distal portion 46 of shaft 44 includes guide element 110 whichacts as a transition surface 110. Transition surface 110 is adistally-facing surface extending radially outwardly and proximally,that is longitudinally away from the tip 136 of distal portion 46. Aseries of spaced-apart, first, proximal energizable tissue separatorelements 130 are positioned along transition surface 110. FIG. 23 is across-sectional view taken along line 23-23 of FIG. 18 and illustratesthe electrical connection of elements 130 to metallic tube 132.

[0068] FIGS. 24A-24H illustrate alternative embodiments of firstelements 130. Elements 130A have extended longitudinal lengths, ascompared with the essentially circular elements 130 of FIGS. 18 and 23.It is believed that the extended lengths of element 130A may be usefulfor reducing the penetration force needed for placement at the targetsite. The FIG. 24A embodiment is the presently preferred embodiment.Element 130B comprises a circumferentially continuous or substantiallycircumferentially continuous element. The circumferentially extendingelement 130B may also be useful for reducing the required penetrationforce. Elements 130C are similar to elements 130 but are located atperipheral region 140 of transition surface 110. Elements 130D and 130E,shown in FIGS. 24D and 24E, are generally V-shaped and serpentine-shapedvariations. Elements 130F and 130G, shown in FIGS. 24F and 24G, extendalong substantially the entire lengths of distal portion 46 in straightand spiral configurations, respectively. FIG. 24H illustrates a furtherembodiment of elements 130H with elements 130H extending radiallyoutwardly from distal portion 46; elements 130H may be retractable andmay have shapes other than the pointed, triangular shape illustrated.While elements 130 are typically formed from metal wires or similarstructure, elements 130 may also be painted, plated or otherwisedeposited on the surface of distal portion 46. A combination of two ormore of the arrangements of element 130 may be useful in appropriatecircumstances. While presently all of elements 130 are supplied withequal energy levels, different energy levels may be supplied. Also, theenergy levels supplied may be varied over time or according to theresistance to the passage of separator wire portion 56 through thetissue. Also, energy to elements 130 may be turned on as needed at thediscretion of the user.

[0069] Distal portion 46 is hollow and contains an electricallyconductive, metallic tube 132 defining an opening 134 at the tip 136 ofdistal portion 46. The outer, annular edge of tube 132 acts as a second,distal energizable tissue separator element 138. Both first element 130and second element 138 are selectively coupleable to one or moreappropriate energy sources to aid movement of distal portion 46 throughtissue to the target site.

[0070]FIGS. 25 and 26 illustrate the hook wires 100, which act as tissueholding elements, extending through openings 142 formed within distalportion 46 of shaft 44. Hook wires 100 are preferably sized, positionedand shaped to engage separated tissue section 80 at about its center ofmass. While two hook wires 100 are shown in this embodiment, a greateror lesser number may also be used. Also, hook wires 100 having differentsizes and shapes may be used. Hook wires 100 may also be located atdifferent axial positions and may be energizable to aid movement throughtissue.

[0071]FIGS. 25, 27 and 27A illustrate the passage of separator wireportion 56 through proximal and distal channels 146, 148 formed indistal shaft portion 46. Distal portion 46 defines a base surface 150extending along the bottoms of channels 146 and 148 and extendingbetween channels 146 and 148. Separator wire portion 56 lies againstbase surface 150 when in a retracted state. As shown best in FIGS. 27and 27A, the central portion 152 of base surface 150 is convex so thatwhen separator wire portion 56 is in the retracted state, a centralportion of wire portion 56 lies along a convex line, that is a line thatbows slightly outwardly. Therefore when tissue separator device 54 ismoved distally, separator wire portion 56 is predisposed to moveradially outwardly in the desired manner. The amount of force needed tobe applied to device 54 may also be reduced by the use of convex centralportion 152.

[0072]FIG. 28 illustrates a further alternative embodiment to theembodiment of FIG. 18 comprising three separator wire portions 56, asopposed to one in FIG. 18, one wire portion 56 being shown in anoperational state and the other two wire portions 56 in retracted statesand adjacent base surfaces 150. This is suggested in FIG. 29B. Anotherdifference from the embodiment of FIG. 18 is that the function of first,proximal energizable tissue separator elements 130 has been replaced byenergizing the three separator wire portions 56 when the device isdirected through tissue to a target site with wire portions 56 inretracted states. This is suggested in FIG. 29A. Once at the target sitethe physician may decide to move one, two or all three of separator wireportions 56 from the retracted state to the operational state dependingon various factors, such as the characteristics of the tissue and thenumber of pieces tissue section 80 is to be divided into.

[0073] Distal portion 46, in the embodiment of FIGS. 18-29B, comprises aproximal element 154, a body portion 156 and tip 136, tip 136 acting asan end cap. FIG. 27 illustrates the interengagement of elements 154, 156and 136. Elements 154, 156 and 136 are configured to promote simpleassembly. Assembly may take place by simply stacking each element inorder over central tube 132, the parts being held in place distally bythe flared end 138 of the tube. Elements 154, 156 and 136 are preferablyelectrically non-conductive. Elements 154 and 156 are typically madefrom the medical grade ceramic material, such as A₂O₃ or zirconia, whiletip 136 is typically made from a medical grade polymer, such as PEEK orpolyimide.

[0074] The amount of force required for the passage of a needle, orother tissue-penetrating element, such as distal portion 46 of shaft 44,through tissue often changes because the tissue characteristics oftenchanges between the point of entry and the target site. If thetissue-penetrating element must pass through a hard or otherwisedifficult-to-penetrate tissue region, the amount of force needed topenetrate the hard tissue region may be sufficiently great to, forexample, cause the tissue-penetrating element to buckle. Even if thetissue-penetrating element has sufficient columnar strength to resistbuckling, the amount of force required may be sufficient to cause thetissue to be deformed making it difficult to position the tip of thetissue-penetrating element at the target site. Also, once the tip haspassed through the difficult-to-penetrate tissue region, the amount offorce needed to do so may tend to cause the tip of thetissue-penetrating element to be inserted much farther than desiredcausing unintended tissue trauma and possibly injuring adjacent organs.

[0075]FIG. 30 illustrates, in schematic form, a tissue-penetratingassembly 160 comprising broadly a tissue-penetrating subassembly 162coupled to a tissue-energizing circuit 164 and a force-sensitive switch166 operably coupled to the tissue-penetrating subassembly. Thesubassembly 162 comprises a handle assembly 168, or other supportassembly, including a handle 170, a handle extension 172 extendingrigidly from handle 170, and a needle clamp 172 mounted to handle 170 ata pivot 176. Subassembly 162 also includes a needle 178, or othertissue-penetrating device, secured to and extending from needle clamp174. Needle 178 includes a needle shaft 180 covered by electricalinstallation 182 along most of its length. Electrical installation 182helps to concentrate the tissue-penetrating energy at the tip 184 ofneedle 178, tip 184 having a tissue-separating surface 185.

[0076] Force-sensitive switch 166 includes a compression spring 186captured between needle clamp 174 and handle extension 172. Assembly 160also includes an arming switch 188 mounted to handle 170, switch 188including an arm 190 mounted to handle 170 at a pivot 192. Switch 188also includes an arming compression spring 194 captured between arm 190and handle extension 172. The use of arming switch 188 helps to enhancethe safety of assembly 160 by helping to prevent the inadvertentconnection of needle 178 to RF generator 200. Circuit 164 includes apair of leads 196, 198 electrically connected to needle clamp 174, andthus needle tip 184, and to arm 190 through pivots 176, 192,respectively. Circuit 164 also comprises an RF generator 200, from whichleads 196, 198 extend, and a return cable 202 coupling generator 200 toa return pad 204. An electrical conductor 206 is mounted to handleextension 172 and has electrical contact surfaces 208, 210 positionedopposite the corresponding surfaces of needle shaft 180 and arm 190. Anarming button 212 is mounted to arm 190 to permit the user to armassembly 116 by pressing on arming button 212 to cause arm 190 tocontact surface 210. With the device now armed, needle 178 is directedinto tissue, exemplified by three layers of tissue, including softtissue layers 214 and 218 and hard or otherwise difficult-to-penetratetissue layer 216. Upon encountering hard tissue layer 216, the forceneeded to penetrate tissue layer 216 is sufficient to compress spring186 and cause needle shaft 180 to contact electrical contact surface 208thus completing the circuit to RF generator 200. At this point RFgenerator 200 can supply energy to surface 185 at tip 184 permittingneedle 178 to pass through hard tissue 216 without excessive force. Oncetip 184 has passed through hard tissue layer 216, the force on needle178 decreases to permit spring 186 to separate needle shaft 180 fromcontact surface 208 so to stop supplying RF energy to tissue separatorsurface 185.

[0077] Tissue-penetrating assembly 160 can be used to aid the insertionof a simple needle into tissue. However, the tissue-penetratinginvention also can be incorporated into other devices includingtissue-penetrating elements, such as the embodiments discussed aboveincluding shaft 44 and a target tissue localization device disclosed inU.S. Pat. No. 6,179,860.

[0078] FIGS. 31-39 illustrate further aspects of the invention in whichtissue separator assembly 10 is combined with an elongated coupler 220and a tissue localization assembly 222 to arrive at a tissue localizingand separating assembly 224. Tissue localization assembly 222 may be ofthe type disclosed in U.S. Pat. No. 6,179,860. Assembly 222 is showndeployed within a patient 226 with localization device to 112 in aradially expanded, deployed condition. Assembly 222 includes a sheath228 (see FIG. 32) within which a pull wire 230 is slidably housed. Therelative axial movement of sheath 228 and pull wire 230 causeslocalization device 112 to radially expand and radially contract. Theproximal end 232 of pull wire 230 is a recurved end 232 (see FIGS. 32,34) for engagement by coupler 220 as discussed below.

[0079] Coupler 220 is a flexible wire having a coupler loop 234 at itsdistal end and an enlarged proximal end 236. Coupler 220 passes throughshaft 44 (see FIGS. 2, 32) of catheter assembly 12. Coupler loop 234 isused to join coupler 220 to the recurved end 232 of pull wire 230; thisis shown in FIGS. 31-34. After being so joined, tissue separatorassembly 10 is moved distally along coupler 220, while the user graspsend 236 to maintain tension on the tissue localization assembly 220,causing the joined ends 232, 234 to pass into shaft 44 thus dockingtissue localization assembly 222 to tissue separator assembly 10.Continued distal movement of assembly 10 causes catheter assembly 12 toenter patient 226 and pass along the tissue track created by tissuelocalization assembly 222 until tip 136 of distal portion 46 of shaft 44is properly positioned relative to localization device 112. Properpositioning is visually indicated to the user by a length of tube 233,typically colored red and affixed to coupler 220, becoming exposed afterexiting the proximal end opening 235 of handle 14 as shown in FIGS.35A-35C. When properly positioned, see FIG. 35C, a locking spring clip237, located on handle 14 adjacent to proximal end opening 235, springsback from its biased position of FIG. 35B to its unbiased position ofFIGS. 35A and 35C to prevent tube 237 from inadvertently reenteringhandle 14. When so positioned, tissue localization assembly 222 becomesat least temporarily locked or fixed to tissue separator assembly 10 toprevent the inadvertent relative axial movement between localizationdevice 112 and assembly 10. Of course other locking mechanisms, such asa spring finger carried by assembly 220 and engageable with handle 14,can also be used to lock assemblies 10, 222 to one another.

[0080]FIG. 36 is an enlarged view of the distal portion of assembly 224of FIG. 35 after separator wire portion 56 has been radially expandedand rotated, to create a separated tissue section 80, and after hookwire 100 has been deployed to engage the separated tissue section 80. Ithas been found to be desirable to leave a space, indicated generally asdistance 238, between localization device 112 and separated tissuesection 80. FIG. 37 illustrates the assembly of FIG. 36 after introducersheath 42 has been moved proximally a short distance to expose outer end106 of tubular braided element 104. FIG. 38 is a somewhat generalizedillustration of the movement of tubular braided element 104 in a distaldirection within patient 226 with the tubular braided element initiallygenerally following the outline of separated tissue section 80 and outerend 106 generally axially aligned with localization device 112. Itshould be noted that the movement of outer end 106 of tubular braidedelement 104 will generally following the path indicated until it reachesposition 240. Following position 240, the path outer end 106 takes willlargely depend on the physical characteristics of the tissue throughwhich is passing. However, the path illustrated is typical. Separatedtissue section 80 is then removed from patient 226 by simultaneouslypulling the entire assembly shown in FIG. 38, including separated tissuesection 80 captured by tubular braided element 104 and localizationdevice 112, secured by coupler 220, back along the tissue track. Duringthis movement tubular braided element 104 has a tendency to elongateaxially to a reduced diameter, more cylindrical form thus reducingpotential tissue trauma along the tissue track and through the accessopening at the beginning of the tissue track.

[0081]FIG. 39 illustrates the assembly of FIG. 38 after having beenremoved from patient 226 with outer end 106 of tubular braided element104 returned to its relaxed state and tissue specimen 80 retained bytubular braided element 104 and localization device 112. As suggested inFIG. 39, tubular braided element 104, when in a relaxed state, has agenerally trumpet shape with outer end 106 flaring outwardly. It hasbeen found that this trumpet shape helps to guide tubular braidedelement 104 around separated tissue section 80, especially during itsinitial movement from introducer sheath 42.

[0082] FIGS. 40-45 illustrate a preferred method of making tubularbraided element 104. Tubular braided element 104 is sized according tothe size of the tissue specimen being removed so that the number ofelements, sizes and other specifications discussed below may be variedaccording to a particular circumstance. FIG. 40 illustrates the shape ofa length of tubular braided material 244 after it has been stretchedover a cylindrical mandrel (not shown) having an enlarged (20.5 mmdiameter by 50 mm long) central portion in this embodiment. Material244, prior to being stretched over the mandrel, is supplied in acontinuous length and cut to size for the mandrel and a startingdiameter of {fraction (5/16)}″ or 8 mm. Material 244 is made ofmonofilament polyester fibers having a diameter of 0.10 inch (0.25 mm)The braid consists of 56 monofilaments and is made on 56 carrierbraider. The braid, when formed in continuous lengths, maintains anapproximate {fraction (5/16)}″ (8 mm) internal diameter. The braid angleis held fixed during the braiding operation, and was chosen for thisapplication because a small shortening in axial length results in arapid change in diameter. The enlarged central portion of the mandrelcorresponds to the shape of tubular braided material 244, that is it iscylindrical with generally hemispherical ends. FIG. 41 illustrates thestructure of FIG. 40 after one end of the mandrel and tubular braidedmaterial 244 has been dipped into a silicone compound. The dippedstructure is then cured, typically in an oven, to create a silicone filmor web 246 covering one end of tubular braided material 244. Aftercuring, the dipped, cured structure 248 is removed from the mandrel bybeing pulled over the mandrel from left to right in FIG. 41. FIG. 42illustrates the open mesh end 250 of the dipped, cured structure 248being pulled back into the dipped end to create the dual-wall tubularbraided element 104 shown in FIG. 43. FIG. 43 illustrates tubularbraided element 104 being mounted to the distal end of actuator tube 43.FIGS. 44 and 45 show the proximal end of tubular braided element 104being secured to the distal end of actuator tube 43 by a length of heatshrink tubing 252 and an adhesive to create a tissue-surroundingassembly 254. Dual-wall tubular braided element 104 has an outer wall256 substantially completely covered with silicone web 246, and innerwall 258 at least substantially free of the silicone web material, anopen outer end 106 covered with silicone web 246.

[0083] Silicone web 246 serves at least two functions. It helps maintainthe trumpet shape of tubular braided element 104 in its relaxed statewhile permitting the tubular braided element to radially expand andradially contract from the trumpet shape. It also helps to preventpassage of tissue through tubular braided element 104 during removal ofseparated tissue section 80. This helps to prevent contamination alongthe tissue track during tissue removal procedures. While tubular braidedelement 104 could be made as a single layer, that is without open meshend 250 being pulled back into the structure, it has been found thatdoing so helps to maintain a softer leading edge at outer end 106 oftubular braided element 104. The general trumpet shape shown in FIGS.43-45 occurs as a natural result of the forming process illustrated anddescribed.

[0084] The following discussion of the development of the currentembodiment of braided element 104 may be useful in appreciating itsvarious features and advantages. The presently preferred embodiment ofbraided element 104 comprises a tubular sleeve of braided polyester(PET-polyethylene terephthalate) monofilament folded over itself to forma smooth end. The open weave construction allows it to enlarge toseveral times its original diameter. The outer braided layer is coatedwith silicone.

[0085] Early braided element prototypes consisted of Nitinol braidedtubing. The wire diameter, braid angle and number of wires that comprisethe braid were explored. These properties affect the strength of thebraided element. The braided element must have enough stiffness andcolumnar strength to overcome the forces acting against it as it isdeployed in the tissue. However, if it is too rigid, it may push theseparated tissue section further into the cut cavity. Non-braided formswere also considered, such as Nitinol wire placed axially along thelengths of the axis, supported by coating or other rigid members. Thecombination of wire diameter, braid angle, and number of wires alsoaffects the retracted properties of the braided element. In itsundeployed state, the braided element was designed to fit inside a 6 mmsheath. Some of the Nitinol prototypes that were fabricated seemed tohave adequate strength and stiffness, and fit within a 6 mm sheath.However, because of other factors discussed below, a PET braid presentlypreferred over a Nitinol braid.

[0086] There are several factors that interact to effect columnarstrength. Braid angle, number of filaments, and filament materialstiffness and diameter are the main determinants. Axial orientation,greater number and stiffer filaments all combine for greater columnarstrength. The presently preferred material for braided element 104 is0.010″ (0.25 mm) diameter monofilament. The number of monofilaments inthe braid was chosen to optimize the mechanical properties of braidedelement 104. Increasing the number of filaments will create the oppositeeffect- the columnar strength will be reduced thus increasing the chanceof buckling. Fewer filaments creates an increase in spacing between thefilaments as the braided element expands from retracted to deployed. Ifthe spacing becomes too large, the coating may tear. Also, a braidedelement constructed with a more axially oriented braid angle will takeup much more length in the retracted state and therefore require agreater amount of travel to deploy. The number of filaments was chosento optimize braided element strength, spacing between filaments, andamount of deployment travel.

[0087] It is presently preferred that the distal end of the braidedelement, that is the end that first comes into contact with the tissue,be smooth. It was discovered at a braided element with jagged or sharpedge may get caught in the tissue and fail to slide into the cut tissueinterface around the separated tissue section. For the Nitinol braid,various methods of terminating the lose wires were explored, such assoldering, brazing, or bonding balls at the wire ends, or folding eachsingle wire over. These methods were not very successful. For the ballsto be atraumatic, they need to be of considerable size. The balls orfolded-over ends increase the diameter of the retracted braided element,making it difficult to fit inside a sheath. This led to concepts of‘roll-over’ and ‘double layer’ braided elements. For both concepts, thetubular braid is folded over itself to form a two-layered braidedelement with folded-over, smooth ends. For a ‘double layer’ braidedelement, the two layers are bonded together at the proximal end. Thetwo-layered Nitinol braided elements that were prototyped showedpromising characteristics. However the folded-over ends provided toomuch bulge and made it difficult or impossible to retract into a 6 mmdiameter sheath. The PET braid, on the other hand, forms a nice creasewhen the braid is folded over, and is easily retracted into the sheath.For deployment, the outer layer is pushed forward and allowed to slideover the inner layer. This embodiment has potential but is not thepresently preferred embodiment.

[0088] The shape of the braided element also affects its functionality.Braided element prototypes of many different shapes were tested, such as“bullet”, “cone”, and “bell” or “trumpet” profiles of varying diameters.A desirable characteristic of braided element 104 is that the braidedelement flares open as it is initially deployed, so that it ispredisposed to expand around the biopsy sample rather than push thesample further into the cavity. The shape of braided element 104 hasbeen optimized to maximize the amount that it flares open duringdeployment.

[0089] The braided element is currently coated with a two-componentsilicone elastomer. Some polyurethane coatings were investigated also,but did not perform as well as silicone coatings during preliminarytesting. The silicone coating was chosen because of its high tearstrength and elasticity. From the retracted state to the fully deployedstate, the diameter of braided element 104 may expand as much as 300%.The braided element may have a snare at the distal end to aid incapturing the sample.

[0090] Modification and variation can be made to the disclosedembodiments without departing from the subject of the invention asdefined in the following claims. For example, lead screw 52 could behollow to permit actuator shaft 114, or other medical devices, to passtherethrough and into a lumen within shaft 44. While base surface 150 isshown to have a smoothly curving shape, surface 150 may have othershapes, such as a discontinuous surface shape, a flat surface shape withone or more projections providing the desired bow in the separator wireportion 56, or a combination thereof. Braided element 104 may be made ofother materials and by other processes than those disclosed.

[0091] Any and all patents, patent applications and printed publicationsreferred to above are hereby incorporated by reference.

What is claimed is:
 1. A tissue-separating catheter assembly comprising:a rotatable shaft having a distal shaft portion; a tissue separatordevice extending along the shaft and having a distal separator part atthe distal shaft portion movable between a retracted state, towards thedistal shaft portion, and an outwardly extending, operational state,away from the distal shaft portion; said shaft comprising a tip; thedistal shaft portion comprising a distally-facing transition surface ata proximal end of the distal shaft portion, said transition surfaceextending radially outwardly and longitudinally away from said tip; afirst energizable tissue separator element at the transition surface; asecond energizable tissue separator element at or near the tip; and saidfirst and second tissue separator elements adapted to aid movement ofthe distal shaft portion through tissue and to a target site.
 2. Thecatheter assembly according to claim 1 wherein the transition surfacecomprises a peripheral region and the first energizable tissue separatorelement is located adjacent to the peripheral region.
 3. The catheterassembly according to claim 1 wherein the transition surface comprises aperipheral region and the first energizable tissue separator element islocated at the peripheral region.
 4. The catheter assembly according toclaim 1 wherein the first energizable tissue separator element comprisesat least one exposed energizable surface.
 5. The catheter assemblyaccording to claim 1 wherein the first energizable tissue separatorelement comprises a plurality of energizable surfaces.
 6. The catheterassembly according to claim 5 wherein the energizable surfaces arelocated at circumferentially spaced-apart positions along the transitionsurface.
 7. The catheter assembly according to claim 1 wherein the firstenergizable tissue separator element comprises a continuous,circumferentially-extending energizable surface.
 8. The catheterassembly according to claim 1 wherein the second energizable tissueseparator element comprises an annular energizable surface.
 9. Thecatheter assembly according to claim 1 wherein the distal separator partis energizable.
 10. The catheter assembly according to claim 1 whereinthe distal shaft portion comprises a base surface, the distal separatorpart being in contact with the base surface when in the retracted state.11. The catheter assembly according to claim 10 wherein at least aportion of the base surface is convex.
 12. The catheter assemblyaccording to claim 1 wherein the distal shaft portion comprises achannel housing at least a portion of the distal separator part.
 13. Thecatheter assembly according to claim 1 wherein the distal shaft portioncomprises a proximal channel and a distal channel housing proximal anddistal portions of the distal separator part when the distal separatorpart is in the retracted state.
 14. The catheter assembly according toclaim 1 wherein: the distal shaft portion has a base surface, the distalseparator part being in contact with the base surface when in theretracted state; and the base surface having a convex central portion.15. The catheter assembly according to claim 31 wherein: the distalshaft portion comprises a proximal channel and a distal channel housingproximal and distal portions of the distal separator part when thedistal separator part is in the retracted state; the distal shaftportion has a base surface, the distal separator part being in contactwith the base surface when in the retracted state; and at least aportion of the base surface being located between the proximal channeland the distal channel, said portion being convex.
 16. The catheterassembly according to claim 1 wherein the distal separator partcomprises a flexible, electrically conductive wire.
 17. The catheterassembly according to claim 1 further comprising a tissue sectionholding element at the distal shaft portion, said holding elementmovable from a retracted condition to an extended, tissue-engagingcondition so to help secure a separated tissue section to the catheterassembly.
 18. The catheter assembly according to claim 17 wherein thetissue section holding element comprises a wire having a pre-curveddistal end.
 19. A tissue-separating catheter assembly comprising: ashaft having a distal shaft portion; a tissue separator device extendingalong the shaft and having a distal separator part at the distal shaftportion movable between a retracted state, towards the distal shaftportion, and an outwardly extending, operational state, away from thedistal shaft portion; and first and second energizable tissue separatormeans for aiding movement of the distal shaft portion through tissue andto a target site, said first and second movement aiding means locatedgenerally proximal and distal of the distal separator part of the tissueseparator device, respectively.
 20. A method for accessing a target sitewithin a patient comprising: selecting a tissue-separating catheterassembly comprising: a rotatable shaft having a distal shaft portion; atissue separator device extending along the shaft and having a distalseparator part at the distal shaft portion movable between a retractedstate, towards the distal shaft portion, and an outwardly extending,operational state, away from the distal shaft portion; said shaftcomprising a tip; the distal shaft portion comprising a distally-facingtransition surface at a proximal end of the distal shaft portion, saidtransition surface extending radially outwardly and longitudinally awayfrom said tip; a first energizable tissue separator element at thetransition surface; and a second energizable tissue separator element atthe tip; directing the distal shaft portion, and the first and secondenergizable tissue separator elements and the distal separator parttherewith, through tissue and to a target site; and energizing saidfirst and second energizable tissue separator elements during at least apart of the directing step so to aid movement of the distal shaftportion through the tissue and to the target site.
 21. The methodaccording to claim 20 wherein the selecting step is carried out with thetransition surface comprising a peripheral region and the firstenergizable tissue separator element being located adjacent to theperipheral region.
 22. The method according to claim 20 wherein theselecting step is carried out with the transition surface comprising aperipheral region and the first energizable tissue separator elementbeing located at the peripheral region.
 23. The method according toclaim 20 wherein the selecting step is carried out with the firstenergizable tissue separator element comprising a plurality of exposedenergizable surfaces.
 24. The catheter according to claim 23 wherein theselecting step is carried out with the exposed energizable surfacesbeing located at circumferentially spaced-apart positions along thetransition surface.
 25. The catheter assembly according to claim 20wherein the selecting step is carried out with the first energizabletissue separator element comprising a continuous,circumferentially-extending exposed energizable surface.
 26. The methodaccording to claim 20 wherein the selecting step is carried out with thesecond energizable tissue separator element comprising an exposed,annular energizable surface.
 27. The method according to claim 20wherein the energizing step comprises energizing the distal separatorpart during at least part of the directing step.
 28. The methodaccording to claim 20 wherein the energizing step is carried out usingRF energy.
 29. A tissue-separating catheter assembly comprising: arotatable shaft having a distal shaft portion; a tissue separator deviceextending along the shaft and having a distal separator part at thedistal shaft portion movable between a retracted state, towards thedistal shaft portion, and an outwardly extending, operational state,away from the distal shaft portion; the distal separator part comprisinga distal separator end; and a pivot joint pivotally connecting thedistal separator end to the distal shaft portion so that said distalseparator end effectively pivots freely at the pivot joint as the distalseparator part moves between the retracted and operational states. 30.The catheter assembly according to claim 29 wherein the pivot jointcomprises a ball-type element at the distal separator end housed withina cavity defined by the distal shaft portion.
 31. The catheter assemblyaccording to claim 29 wherein the distal shaft portion comprises a basesurface, the distal separator part being in contact with the basesurface when in the retracted state.
 32. The catheter assembly accordingto claim 31 wherein at least a portion of the base surface is convex.33. The catheter assembly according to claim 29 wherein the distal shaftportion defines a channel housing at least a portion of the distalseparator part.
 34. The catheter assembly according to claim 29 whereinthe distal shaft portion comprises a proximal channel and a distalchannel housing proximal and distal portions of the distal separatorpart when the distal separator part is in the retracted state.
 35. Thecatheter assembly according to claim 29 wherein: the distal shaftportion comprises a proximal channel and a distal channel housingproximal and distal portions of the distal separator part when thedistal separator part is in the retracted state; the distal shaftportion has a base surface, the distal separator part being in contactwith the base surface when in the retracted state; and at least aportion of the base surface being located between the proximal channeland the distal channel, said portion being convex.
 36. The catheterassembly according to claim 29 wherein the distal separator partcomprises a flexible, electrically conductive wire.
 37. The catheterassembly according to claim 29 further comprising a tissue sectionholding element at the distal shaft portion, said holding elementmovable from a retracted condition to an extended, tissue-engagingcondition so to help secure a separated tissue section to the catheterassembly.
 38. The catheter assembly according to claim 37 wherein thetissue section holding element comprises a hook wire having a pre-curveddistal end.
 39. The catheter according to claim 37 wherein the tissueholding element is an energizable tissue holding element.
 40. A methodfor increasing the volume of a separated tissue section from a patientcomprising: selecting a tissue-separating catheter assembly comprising:a rotatable shaft having a distal shaft portion; a tissue separatordevice extending along the shaft and having a distal separator part atthe distal shaft portion movable between a retracted state, towards thedistal shaft portion, and an outwardly extending, operational state,away from the distal shaft portion; the distal separator part comprisinga distal separator end; and a pivot joint pivotally connecting thedistal separator end to the distal shaft portion so that said distalseparator end effectively pivots freely at the pivot joint as the distalseparator part moves between the retracted and operational states;directing the distal shaft portion, and the distal separator part andthe pivot joint therewith, through tissue and to a target site; movingthe distal separator part through tissue from the retracted state to anoperational state with the distal separator part pivoting at the pivotjoint; rotating the shaft thereby causing the distal separator part inthe operational state to pass through tissue and create a separatedtissue section; and removing the separated tissue section from thepatient.
 41. The method according to claim 40 further comprisingenergizing the distal separator part during the moving and rotatingsteps.
 42. A method for accessing a target site within a patientcomprising: selecting a tissue-separating catheter assembly comprising:a rotatable shaft having a distal shaft portion; a tissue separatordevice extending along the shaft and having a plurality of distalseparator parts at the distal shaft, each said distal separator partbeing positionable at an exposed, retracted state towards the distalshaft portion, at least one of said distal separator parts being movableto an outwardly extending, operational state spaced apart from thedistal shaft portion; and at least some of said distal separator partsbeing energizable in said exposed, retracted state; directing the distalshaft portion and the distal separator parts therewith through tissueand to a target site while the distal separator parts are in saidexposed, retracted states; and energizing said at least some of saiddistal separator parts during at least a part of the directing step soto aid movement of the distal shaft portion through the tissue and tothe target site.
 43. The method according to 42 when the selecting stepis carried out with a catheter assembly comprising at least three distalseparator parts.
 44. The method according to claim 42 when theenergizing step comprises energizing at least three distal separatorparts.
 45. The method according to claim 44 wherein the selecting stepis carried out with said at least three distal separator parts beingcircumferentially evenly spaced apart.
 46. The method according to claim42 wherein the energizing step is carried out using RF energy.
 47. Themethod according to claim 71 wherein the selecting step is carried outwith the distal separator parts comprising longitudinally-extendingwires.